Calcification of the menisci, known as chondrocalcinosis, is not an uncommon problem. Once calcified the menisci are more britlle and are mote likely to tear with trivial activity. The condition can also lead to an acute inflamatory reaction within the joint, similar to gout, and aptly named "pseudogout.
If you do have a large collection of fluid within your knee, your orthopedist may elect to aspirate (drain) the fluid, and send the fluid to the lab for analysis. I usually inject theses knees with cortisone, and start the patient on an oral NSAID. Many of them calm down and do not require further treatment.
For those that remain symptomatic, I perform arthroscopic surgery. At surgery, the calcified menisci are debrided (cleaned up), the inflammed synovium is removed, and the knee is "washed out". Patients do well after arthroscopic treatment and are able to return to full activity quite quickly.
Good Luck!!